Apparatus and methods for making spectroscopic measurements of cathode fall in fluorescent lamps

Abstract

Apparatus and methods are disclosed for measuring cathode fall within a fluorescent lamp that contains an electrode and a gas. A level of cathode fall associated with the electrode may be identified based on an intensity and wavelength of radiation emitted by the gas.

1. Apparatus for measuring cathode fall in a fluorescent lamp that contains an electrode and a gas, the apparatus comprising:
 a radiation detector that receives radiation emitted from the gas, the received radiation having a pre-specified wavelength; and 
 a display that provides a visual representation of an intensity of the received radiation, wherein the intensity of the received radiation corresponds to a level of cathode fall associated with the electrode. 
 
   
   
     2. Apparatus according to  claim 1 , further comprising a power supply that supplies a discharge current to the electrode. 
   
   
     3. Apparatus according to  claim 1 , further comprising a power supply that supplies a heating current to the electrode. 
   
   
     4. Apparatus according to  claim 1 , further comprising a radiation isolator that provides radiation having the pre-specified wavelength to the radiation detector. 
   
   
     5. Apparatus according to  claim 4 , wherein the radiation isolator is adapted to isolate radiation having a specific wavelength, radiation having at least one of a plurality of specific wavelengths, or radiation having a wavelength within a specific range of wavelengths. 
   
   
     6. Apparatus according to  claim 4 , wherein the radiation isolator is one of a spectrometer, a grating polychrometer, a filter, and a prism. 
   
   
     7. Apparatus according to  claim 4 , further comprising a radiation collector that collects radiation emitted from the gas and focuses the radiation onto the radiation isolator. 
   
   
     8. Apparatus according to  claim 1 , wherein the radiation detector is adapted to convert radiation intensity to a voltage and to supply the voltage to the display. 
   
   
     9. Apparatus according to  claim 1 , wherein the radiation detector is one of a photomultiplier tube and a charge-coupled device. 
   
   
     10. Apparatus according to  claim 1 , wherein an onset of emission of said radiation indicates that the cathode fall has exceeded an excitation potential that corresponds to the wavelength of the emitted radiation. 
   
   
     11. Apparatus according to  claim 1 , wherein an onset of emission of the radiation indicates that the cathode fall has exceeded an energy level associated with a metastable state of the gas. 
   
   
     12. Apparatus according to  claim 1 , wherein an onset of emission of the radiation indicates that the cathode fall has exceeded an energy level associated with a 4p state of the gas. 
   
   
     13. Apparatus according to  claim 1 , wherein an onset of emission of the radiation indicates that the cathode fall has exceeded an energy level associated with a 5p state of the gas. 
   
   
     14. Apparatus according to  claim 1 , wherein an onset of emission of the radiation indicates that the cathode fall has exceeded an energy level associated with a metastable state of the gas and that stepwise excitation to a 5p state of the gas is occurring. 
   
   
     15. Apparatus according to  claim 1 , wherein an onset of emission of the radiation indicates that the cathode fall has exceeded an energy level associated with a metastable state of the gas and that stepwise excitation to a 4p state of the gas is occurring. 
   
   
     16. Apparatus according to  claim 1 , wherein an onset of emission of the radiation indicates that the cathode fall has exceeded an energy level associated with a 4p state of the gas and that direct excitation to the 4p state is occurring. 
   
   
     17. Apparatus according to  claim 1 , wherein an onset of emission of the radiation indicates that the cathode fall has exceeded an energy level associated with a 5p state of the gas and that direct excitation to the 5p state is occurring. 
   
   
     18. Apparatus according to  claim 1 , wherein the gas includes at least one of helium, neon, argon, krypton, and xenon. 
   
   
     19. Apparatus according to  claim 1 , wherein the gas includes argon, and the radiation has a wavelength of at least one of about 420.0 nm and about 811.5 nm. 
   
   
     20. A method for measuring cathode fall in a fluorescent lamp that contains an electrode, the method comprising:
 receiving radiation emitted from a negative glow formed proximate the electrode, the received radiation having a pre-specified wavelength; and 
 displaying a visual representation of an intensity of the received radiation, wherein the intensity of the received radiation corresponds to a level of cathode fall associated with the electrode.